AND.... because apparently I'm not done complaining yet....
The abstract states "The model also indicates a temporal transition in the
dinosaur fauna from the Yixian fauna to the Jiufotang fauna in which theropods
decreased ...", but what about Sinotyrannus? It wasn't included, but being a
9-10 meter long tyrannosauroid, it was probably over 3000 kg. That probably
outmasses every other Jiufotang specimen they use, so would surely have a huge
effect on the model. Or the 3 specimens of Yutyrannus, also not included.
That's 1400 kg each of Yixian carnivore. Perhaps worse, there are no sauropods
listed. But Dongbeititan is from the Yixian Formation, and no doubt outmassed
every other Yixian specimen Matsukawa used combined. There are also
Euhelopus-like teeth from the Lujiatun beds of the Yixian Formation (Barrett
and Wang, 2007). Sauropods are also known from the Jiufotang, though
undescribed (Benton et al., 2008). These huge animals would have a huge effect
in any model, which again emphasizes the preservational bias in the Je
hol group so that it doesn't represent the whole ecosystem. And only two(!)
pterosaurs are listed from the entire Jehol- Jeholopterus and Sinopterus. This
is supposedly because these were insectivorous and frugivorous while the others
were piscivorous, but why isn't the listed Dendrorhynchoides also not
insectivorous if Jeholopterus is? If the Witton/Naish azhdarchid feeding model
is right, then the Jehol, chaoyangopterids should be counted as carnivores.
And if piscivory doesn't count as carnivory (as this is a terrestrial model),
then why are any of the birds omnivorous instead of herbivorous or
insectivorous? Sure Confuciusornis and Yanornis ate fish sometimes, but
where's the evidence they ate tetrapods? But the choristoderes are omnivores
in their model too, so anything's possible... :|
Mickey Mortimer
----------------------------------------
> From: mickey_mortimer111@msn.com
> To: dinosaur@usc.edu
> Subject: RE: Jehol Biota food-web models + Middle Jurassic Daohugou plants +
> more papers
> Date: Mon, 20 Oct 2014 20:31:26 -0700
>
> Maybe I'm missing something, but the number of specimens listed for each
> taxon is WAY off, as listed in their Table 5. For example, the specimen
> count for Caudipteryx sp. is listed as 2, but 6 have been published.
> Ironically, they would have to know of at least 3 specimens, since the use of
> 'sp.' instead of zoui in their table indicates multiple species were being
> counted, and there were 2 C. zoui specimens published in the original
> description before C. dongi's specimen was published. Similarly, Dilong's
> specimen count is listed as 1, even though four specimens were described in
> the original paper. Beipiaosaurus- 1 listed instead of 2, Huaxiagnathus 1
> instead of 2, Mei 1 instead of 2, Sinornithosaurus 2 instead of more than 5
> at least, Sinosauropteryx 2 instead of 4, Sinovenator 1 instead of 4,
> Microraptor 2 instead of 25, 'Epidendorosaurus' is probably not even from the
> Yixian Formation... The birds are even worse. Only 8 Confuciusornis?! Over
> 140 specimens have been separ
ately listed in the literature and several hundred were reported to exist even
as early as 1998. So that biomass would go from 34.4 kg per square km to 602
kg at bare minimum. Surely that would have some effect on the calculations?
Zheng et al. (2011) reported over 100 Jeholornis, nearly 100 Sapeornis and over
two dozen Hongshanornis, but Matsukawa et al. only list 3, 3, and er... none
respectively. Who knows why Hongshanornis is missing, but they have one Gansus
specimen listed despite it being from a completely different formation. And
being known from at least 70 specimens, not one. Otogornis is also listed as
Jiufotang, but is also from a different locality. The masses are also way off,
at least in comparison to each other. For example, Yixianosaurus has a humerus
89 mm long, while Sinovenator's is 71 mm, so cubing the ratio would make
Yixianosaurus about twice the weight of Sinovenator. But it's listed as five
times heavier in the table. Finally, the 'feeding modes' l
isted are often problematic. Every Jehol bi!
rd was a
omnivore, eh? Despite the wildly varying dentition and beak shapes. Even more
ridiculously, all of the Jehol amphibians were omnivores?! I'm no amphibian
expert, but I was under the impression almost all amphibians are basically
carnivores or insectivores, with the exception of algae-scraping tadpoles.
>
> In conclusion, unless I'm missing something obvious about the paper, three of
> the basic units of data Matsukawa et al. base their model on are completely
> unreliable. A study like this cannot depend on published numbers of
> specimens to approximate population ratios because after a taxon is
> described, only a few other specimens are usually noted in the literature.
> What you'd need to do is examine a huge collection, like the thousand or so
> Jehol coelurosaurs in the STM, and hope there was little bias in what was
> collected. Even then, it only shows you what died in the lakes, not what
> lived in the ecosystem. Do we really think 80% of Yixian dinosaurs were
> Confuciusornis?
>
> Mickey Mortimer
>
>
>> Masaki Matsukawa, Kenichiro Shibata, Kenta Sato, Xu Xing and Martin G.
>> Lockley (2014)
>> The Early Cretaceous terrestrial ecosystems of the Jehol Biota based
>> on food-web and energy-flow models.
>> Biological Journal of the Linnean Society 113(3): 836–853
>> DOI: 10.1111/bij.12368
>> http://onlinelibrary.wiley.com/doi/10.1111/bij.12368/abstract
>>
>> The ancient terrestrial ecosystems of the Lower Cretaceous Yixian
>> Formation and the Jiufotang Formation, consecutive components of the
>> Jehol Group in Northeast China were reconstructed using an energy-flow
>> and food-web model. This model can be used to quantitatively estimate
>> population densities for ancient terrestrial vertebrates based on food
>> webs, net primary productivity, and three categories of
>> energy-transfer efficiency. The results indicate that densities
>> reached 866 individuals km−2 and 4122 individuals km−2 in two
>> ecosystems, respectively. The main component of the vertebrate fauna
>> of the Yixian Formation consisted of large herbivorous dinosaurs,
>> while much smaller avians dominated the Jiufotang fauna. The model
>> also indicates a temporal transition in the dinosaur fauna from the
>> Yixian fauna to the Jiufotang fauna in which theropods decreased and
>> ceratopsids became more abundant. We then compared these estimates of
>> biodiversity with the Early Cretaceous Choyr fauna of Mongolia, and
>> Tetori fauna of Japan using Simpson's diversity indices. Those
>> indices, based on biomass, indicate that the biodiversities of the
>> Jehol fauna lay between those of the Choyr and Tetori faunas. This
>> range in biodiversity seems attributable to fundamental differences in
>> vegetation and the environment.
>